Conventionally, a flat knitting machine 1 such as schematically shown in FIGS. 11 and 12 is provided with a yarn feeding apparatus 6, for example, on a side cover 5 that is on one end side of a needle bed in a longitudinal direction so that a knitting yarn 4 is supplied from a yarn feeding port of a yarn feeding member 3 to knitting needles while knitting a knitting fabric 2. The yarn feeding apparatus 6 supplies the knitting yarn 4 in accordance with a carriage (not shown) moving along the needle-bed so that a knitting operation of the knitting fabric is performed for one course. The carriage is provided with a cam mechanism for letting knitting needles perform a knitting operation, and is further provided with a mechanism for moving the yarn feeding member 3 from which the knitting yarn 4 is supplied to the knitting needles that are currently performing a knitting operation. Generally, a plurality of yarn feeding members 3 and yarn feeding apparatuses 6 are provided, so that a plurality kinds of knitting yarns 4 can be supplied. However, in this specification, the structure is simplified and only one for each is shown.
A buffer rod 7 is included in the yarn feeding apparatus 6, and serves to temporarily store the knitting yarn 4 and to apply a tension to the knitting yarn 4. The buffer rod 7 can displace the front end side 9 thereof by swinging around a base end side 8 that is supported by the side cover 5. The front end side 9 of the buffer rod 7 pulls the knitting yarn 4 by a force of a spring, and is stable when the force of the spring is balanced with the tension of the knitting yarn 4. A length measuring roller 10 is provided on a path on which the knitting yarn 4 is supplied, and measures the length of the knitting yarn 4 that is supplied from the yarn feeding apparatus 6 to the yarn feeding member 3. When a measurement is performed with the measuring roller 10, it is possible to control the stitch density representing an amount that the carriage pulls the knitting needles for knitting the knitting fabric 2, so that the consumption amount of the knitting yarn 4 matches an amount estimated in advance based on knitting data.
FIG. 11 shows the positional relationship of the yarn feeding member 3 in the flat knitting machine 1 when the carriage starts to move from one end side to the other end side of the needle bed, that is, in a direction away from the yarn feeding apparatus 6. FIG. 12 shows the positional relationship of the yarn feeding member 3 when the carriage has moved to the other end side of the needle bed and the yarn feeding member 3 has moved to the end of the knitting fabric 2 on the side away from the yarn feeding apparatus 6. In the flat knitting machine 1, the length of the knitting yarn 4 that is necessary between the yarn feeding apparatus 6 and the yarn feeding member 3 changes in accordance with the positional relationship of the yarn feeding member 3 with respect to the knitting fabric 2.
In the conventional yarn feeding apparatus 6 that stores the knitting yarn 4 and applies a tension to the same, depending on the inclination degree of the buffer rod 7, the buffer rod 7 stores the knitting yarn 4 to the maximum extent when the yarn feeding member 3 is at the end of the knitting fabric 2 on the side of the yarn feeding apparatus 6 as indicated by broken line in FIG. 11. When a knitting operation of the knitting fabric 2 for the next course starts, the carriage moves the yarn feeding member 3 in the direction away from the yarn feeding apparatus 6. The knitting yarn 4 is pulled, and thus the inclination of the buffer rod 7 becomes small as indicated by solid line. As shown in FIG. 12, when the yarn feeding member 3 is moved close to the end of the knitting fabric 2 on the side away from the yarn feeding apparatus 6, the required amount of the knitting yarn 4 decreases, and thus the inclination of the buffer rod 7 again becomes large as indicated by the broken line, so as to pull and store a larger amount of the knitting yarn 4. Since the inclination of the buffer rod 7 corresponds to the tension of the knitting yarn 4, a change in the tension of the knitting yarn 4 becomes large during a knitting operation when the knitting yarn 4 is applied with a tension and is stored by using the inclination of the buffer rod 7.
Japanese Examined Patent Publication JP-B2 2541574, for example, discloses a conventional technique in which a tension is applied to a knitting yarn and spare storage is performed to cope with a drastic change in the tension of the knitting yarn, by using a member corresponding to the buffer rod 7, such as shown in FIGS. 11 and 12, in order to suppress the change in the tension of the yarn while actively sending out the knitting yarn. Japanese Unexamined Patent Publication JP-A 11-500500 (1999) discloses a conventional technique in which the rotation of a spinning wheel for sending out a knitting yarn is controlled before a drastic change in a requirement of the yarn, without using a member corresponding to the buffer rod 7, such as shown in FIGS. 11 and 12, in order to suppress the change in the tension of the yarn.
As described above, in the conventional yarn feeding apparatus 6 such as shown in FIGS. 11 and 12, the required amount of the knitting yarn 4 significantly changes in accordance with a position to which the yarn feeding member 3 has moved while knitting the knitting fabric 2 by using the flat knitting machine 1, and thus the tension of the yarn is also changed in accordance with the requirement of the yarn. A drastic change in a tension of a yarn causes a change in the length of a knitting stitch loop in a knitting width direction of the knitting fabric 2, and thus the quality of the knitting fabric 2 is deteriorated.
The conventional technique disclosed in Japanese Examined Patent Publication JP-B2 2541574 also has a difficulty in coping with a drastic change in a required amount of a yarn that occurs, for example, at an end portion of a knitting fabric. The conventional technique described in Japanese Unexamined Patent Publication JP-A 11-500500 (1999) is expected to be capable of coping with a drastic change in a required amount of a knitting yarn. However, since this conventional technique needs to wind a knitting yarn around a spinning wheel, the spinning wheel becomes large. Flat knitting machines often knit a knitting fabric by using a plurality of yarns, and thus such flat knitting machines need to include a yarn feeding mechanism for each yarn. When flat knitting machines include a plurality of yarn feeding apparatuses each of which uses a large spinning wheel, the flat knitting machines become large.
In the conventional technique shown in FIGS. 11 and 12, even when it is attempted to measure the length of the already supplied knitting yarn 4 with the measuring roller 10 in order to supply the necessary knitting yarn 4 according to knitting data of the knitting fabric 2, the accurate amount of the knitting yarn for the entire width of the knitting fabric 2 cannot be identified. For example, in FIG. 11, which shows a starting point for collecting data, the length of the knitting yarn 4 can be measured accurately only at a position that is inward from the end of the knitting fabric 2 by more than a length L1 that is several centimeters. This is because when the buffer rod 7 is inclined from the state indicated by the solid line to the state indicated by the broken line, also the stored amount of the knitting yarn 4 that is increased when the buffer rod 7 is inclined is measured with the measuring roller 10, and thus the accurate consumption amount of the knitting yarn 4 that is supplied to the knitting fabric 2 becomes unidentified. Furthermore, the amount of the knitting yarn 4 that is supplied when the buffer rod 7 returns from the state indicted by the broken line to the state indicated by the solid line cannot be measured directly with the measuring roller 10. In FIG. 12, which shows an ending point for collecting data, the length of the knitting yarn 4 indicated by broken line cannot be identified. Without identifying the accurate length of the knitting yarn 4, even when the stitch density is controlled so that the consumption amount of the knitting yarn 4 matches an amount that is estimated in advance based on knitting data, a sufficient effect cannot be attained.
The conventional technique in Japanese Examined Patent Publication JP-B2 2541574 or Japanese Unexamined Patent Publication JP-A 11-500500 (1999) does not describe any configuration relating to an accurate estimation of a required amount of a knitting yarn.